中阶梯光栅光谱仪的光学设计

为了在更宽波段范围内获得较高的分辨率,实现全谱直读,对中阶梯光栅光谱仪进行了研究。简述了中阶梯光栅及中阶梯光栅光谱仪的基本原理,分析并比较了这种光谱仪与普通平面闪耀光栅光谱仪的区别。利用光学成像原理与消像差理论设计了Czerney-Turner结构形式的中型高分辨率中阶梯光栅光谱仪原理样机的光学系统。该光学系统工作在原子谱线最为密集的200～500nm波长处;为简化计算,在设计中消除了350nm波长的所有像差;光线对中阶梯光栅在准Littrow条件下入射,以获得高衍射效率;使用折反射棱镜作为交叉色散元件来分离重叠的级次,在CCD探测器上获得了二维光谱面。该光学系统有较好的平场特性及点对点成像能力,在整个工作波长分辨率可达到2000～15000,满足设计要求。该仪器可用于原子发射和吸收光谱的研究工作,通过替换不同的探测器及增加外围电路与软件平台,仪器的工作性能可进一步提高。

Optical design of cross-dispersed echelle spectrograph

In order to acquire high resolution spectra in a wider spectral range, the echelle based spectrographs were researched. The general theories of the echelle gratings and the echelle spectrographs were introduced briefly, and the distinction between echelle spectrograph and common plane grating spectrograph was analyzed and compared. A high-resolution echelle spectrograph of Czerney-Turner(C-T) structure was designed by using principles of optical imaging and aberration,and its wavelength ranges were set to be 200-500 nm which were the most intensive ranges of atomic spectra. To simplify the calculation work, the aberration of 350 nm wavelength beam was eliminated.Furthermore, the incident beam was set to work at a quasi-Littrow angle to acquire high diffraction efficiency. As a cross-disperser, a catadioptric prism was used to separate the overlapped diffraction orders,therefore, a two-dimensional spectral surface was obtained by CCD. The optical system shows the merits of flat field and point-to-point imaging, and its resolution could be 2 000-15 000 in the whole wavelength ranges. This instrument is aimed to research on the absorption and emission spectra of atoms, and can improve its performance by replacing different detectors and adding peripheral circuits and software.